Gibson, 66, who has been ABC's anchor since 2006, will retire from full-time employment altogether, according to ABC News. "It has not been an easy decision to make," Gibson said in an e-mail to the World News staff Wednesday morning. "This has been my professional home for almost 35 years. And I love this news department, and all who work in it, to the depths of my soul."Good Morning Americaanchor Diane Sawyer, 63, will replace Gibson behind the newsdesk beginning in January 2010.

"Diane Sawyer is the right person to succeed Charlie and build on what he has accomplished," ABC News President David Westin said in a statement. "She has an outstanding and varied career in television journalism, beginning with her role as a State Department correspondent and continuing at 60 Minutes, Primetime Live, and most recently Good Morning America."

Westin said Gibson's decision to retire came after several weeks of discussion, during which Gibson persuaded him it was the best move for the veteran newsman. "I respect his decision, just as I respect the enormous contribution he has made to ABC News through the years," Westin said.

Before anchoring World News, Gibson was co-anchor of Good Morning America. He was previously co-anchor of Primetime from 1998 to 2004. Gibson had planned to step down in 2007, but took the anchor's chair after the retirement of former World News anchor Peter Jennings.With Sawyer taking over Gibson's duties, two of the three network evening news broadcasts will now be anchored by women for the first time in television history. Gibson said he would still like to contribute to ABC News occasionally.